Wave Power

ABSTRACT

A wave-powered water vehicle includes a surface float, a submerged swimmer, and a tether which connects the float and the swimmer, so that the swimmer moves up and down as a result of wave motion. The swimmer includes one or more fins which interact with the water as the swimmer moves up and down, and generate forces which propel the vehicle forward. The vehicle, which need not be manned, can carry communication and control equipment so that it can follow a course directed by signals sent to it, and so that it can record or transmit data from sensors on the vehicle.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/753,377, filed Jan. 29, 2013, which is a continuation of U.S. patentapplication Ser. No. 13/199,646, filed Sep. 6, 2011, now U.S. Pat. No.8,376,790, which is a continuation of U.S. patent application Ser. No.12/087,961, filed Feb. 2, 2009, now U.S. Pat. No. 8,043,133, which is anational phase entry lodged Jul. 18, 2008, under 35 U.S.C. §371 based onPCT Patent Application No. PCT/US 2007/001139, filed Jan. 18, 2007.

PCT Patent Application No. PCT/US 2007/001139 is a continuation-in-partof U.S. patent application Ser. No. 11/436,447, filed May 18, 2006, nowU.S. Pat. No. 7,371,136, which claims priority from U.S. ProvisionalPatent Application No. 60/760,893, filed Jan. 20, 2006.

PCT Patent Application No. PCT/US 2007/001139 claims priority from thefollowing U.S. patent applications:

-   -   U.S. Provisional Patent Application No. 60/841,834, filed Sep.        1, 2006;    -   U.S. patent application Ser. No. 11/436,447, filed May 18, 2006,        now U.S. Pat. No. 7,371,136, which claims priority from U.S.        Provisional Patent Application No. 60/760,893, filed Jan. 20,        2006; and    -   U.S. Provisional Patent Application No. 60/760,893, filed Jan.        20, 2006.

The entire disclosure of each of the above applications is incorporatedherein by reference for all purposes.

BACKGROUND OF THE INVENTION

This invention relates to devices and methods which utilize the power ofwaves in water (hereinafter referred to as “wave power”).

As a wave travels along the surface of water, it produces verticalmotion, but no net horizontal motion, of water. The amplitude of thevertical motion decreases logarithmically with depth; at a depth ofabout half the wave length, there is little vertical motion. The speedof currents induced by wind also decreases sharply with depth. A numberof proposals have been made to utilize wave power to do useful work.Reference may be made, for example, to U.S. Pat. Nos. 986,627,1,315,267, 3,312,186, 3,453,981, 3,508,516, 3,845,733, 3,872,819,3,928,967, 4,332,571, 4,371,347, 4,389,843, 4,598,547, 4,684,350,4,842,560, 4,968,273, 5,084,630 and 6,561,856. The entire disclosure ofeach of those patents is incorporated herein by reference for allpurposes.

SUMMARY OF THE INVENTION

In accordance with the present invention, we have discovered novelwave-powered devices, and novel methods using wave-powered devices. Theinvention will be chiefly described with reference to water vehicleswhich travel over the surface of the water when they are placed in waterhaving waves moving across the surface of the water (hereinafterreferred to as “wave-bearing water”). In such vehicles, at least part ofthe wave power moves the float over the surface of the water (theremainder of the wave power, if any, being converted into other usefulforms, or wasted). However, the invention is also useful when the floatis held in a fixed location, e.g., by an anchor or other attachment. Inpreferred embodiments, the invention makes it possible for unmannedwater vehicles to carry out tasks which would be tedious, expensive ordangerous to carry out using vehicles operated by human beings.

In a first preferred aspect, this invention provides a novelwave-powered device which comprises (1) a float, (2) a swimmer, and (3)a tether connecting the float and the swimmer;

-   -   the float, swimmer and tether being such that, when the vehicle        is in still water, (i) the float is on or near the surface of        the water, (ii) the swimmer is submerged below the float,        and (iii) the tether is under tension; and    -   the swimmer comprising        -   (2a) a swimmer body having a longitudinal axis, and        -   (2b) a fin system which (a) is secured to the body, (b)            comprises a fin, and (c) when the device is in wave-bearing            water,            -   (i) has a configuration which changes as a result of the                wave motion, and            -   (ii) interacts with the water to generate forces which                tend to move the swimmer in a direction having a                horizontal component (hereinafter referred to simply as                “in a horizontal direction”).

The term “fin” is used herein to denote a component comprising agenerally laminar surface against which, when the wave-powered device isin wave-bearing water, the water exerts pressure sufficient tosubstantially influence the movement of the swimmer. In many cases, thewater vehicle includes two or more fins, which may be the same ordifferent, secured to different points on the swimmer body. The“longitudinal axis” of the swimmer body lies in the generally verticalplane along which the swimmer moves when the device is in wave-bearingwater.

The fin system preferably has at least one of (i.e., one or more of) thefollowing characteristics:

-   -   (A) It comprises a fin, for example a generally laminar fin,        which rotates about an axis of rotation (e.g., an axis of        rotation generally transverse to the longitudinal axis of the        swimmer body), the axis of rotation having a spatial        relationship to the swimmer body which changes when the device        is in wave-bearing water.    -   (B) It comprises (i) a fin, for example a generally laminar fin,        which rotates about an axis of rotation (e.g., an axis of        rotation generally transverse to the longitudinal axis of the        swimmer body), and (ii) an elastic component (e.g., a metal coil        spring, a metal leaf spring, a metal torsion bar, or an        elastomeric component such as a natural or artificial rubber        band) which is not part of the fin, and which deforms        elastically and thus influences changes in the configuration of        the fin system when the device is in wave-bearing water.    -   (C) It comprises a fin, for example a generally laminar and        elastically deformable fin, having a leading edge which        comprises (i) a relatively rigid central section which has a        fixed spatial relationship with the swimmer body (including the        possibility that the central section rotates about an axis of        rotation having a fixed spatial relationship with the swimmer        body), and (ii) relatively deformable outboard sections.    -   (D) It comprises two generally laminar fins, for example two        generally laminar and elastically deformable fins which are        mirror images of each other, and each of which rotates about an        axis of rotation generally aligned with the longitudinal axis of        the swimmer body (such fins operate in a manner similar to the        pectoral fins on a fish or the wings on a bird, and are referred        to herein as “pectoral” fins).

The tether preferably comprises one or both of the followingcharacteristics:

-   -   (E) It comprises an elastically deformable member.    -   (F) It comprises a component which transmits data and/or        electrical power.

The swimmer body preferably comprises one or more of the followingcharacteristics:

-   -   (G) It comprises a substantially rigid fore section, a        midsection which is relatively flexible in the vertical plane,        and a substantially rigid aft section, the tether being        attached, for example, to the fore section, and the fin system        being attached, for example, to the fore section.    -   (H) It comprises one or more components selected from electrical        equipment, communications equipment, recording equipment,        control electronics, steering equipment, and sensors.    -   (I) It comprises one or more substantially vertical fins which        influence the orientation of the swimmer body in the horizontal        plane. Such fins can help to balance the drag forces and to        limit rotation of the swimmer when it is pulled sideways by the        tether. In one embodiment, the swimmer body comprises a fixed        leading fin and a trailing fin which can be actuated to steer        the swimmer. In a similar embodiment, a part of the swimmer body        has a relatively small horizontal dimension and a relatively        large vertical dimension; for example, such a part, if at the        trailing end of the swimmer body, could be actuated to steer the        swimmer.    -   (J) It comprises a generally tubular housing, with pectoral fins        which extend either side of the body;

When reference is made herein to a fin or other component which rotatesabout an axis of rotation, or to a component which is rotatably mountedor rotatably secured, this includes not only the possibility that therotation is about a single axis, but also the possibility that therotation results from rotation about two or more axes (which may be, butneed not be, parallel to each other), and the possibility that therotation involves a continuous relative motion of adjacent parts of thefin or other component, as for example when one part of a flexible finis fixed and the rest of the flexible fin moves relative to (i.e.,“rotates about”) the fixed part.

In a second preferred aspect, this invention provides a wave-poweredwater vehicle which comprises (1) a float, (2) a swimmer, (3) a tetherconnecting the float and the swimmer, and (4) a computer system;

the float, swimmer and tether being such that, when the vehicle is instill water,

-   -   (i) the float is on or near the surface of the water,    -   (ii) the swimmer is submerged below the float, and (iii) the        tether is under tension; the swimmer, when the vehicle is in        wave-bearing water, interacting with the water to generate        forces which move the vehicle in a horizontal direction;    -   the float comprising a satellite-referenced position sensor;    -   the swimmer comprising (a) a sensor which senses direction in a        horizontal plane, and (b) a steering actuator; and    -   the computer system (a) being linked to the position sensor, the        horizontal sensor and the rudder, and (b) containing, or being        programmable to contain, instructions to control the steering        actuator in response to signals received from the position        sensor and the horizontal sensor, or in response to signals        received from a sensor on the vehicle. In the water vehicles of        the second aspect of the invention, the swimmer preferably        comprises a body and a fin system according to the first aspect        of the invention, but can comprise a different means for        generating forces which move the vehicle in a horizontal        direction.

The water vehicles of the invention often comprise a single float and asingle swimmer, and the invention will be chiefly described withreference to such water vehicles. However, the invention includes thepossibility that there is more than one float, and/or more than oneswimmer, for example a single float attached to a plurality of swimmers,the swimmers preferably being axially aligned, by a plurality oftethers.

In a third preferred aspect, this invention provides a method ofutilizing wave power which comprises placing a device according to thefirst or second preferred aspect of the invention in a body of waterwhich has or which is expected to have water waves traveling across itssurface.

In a fourth preferred aspect, this invention provides a method ofobtaining information which comprises receiving signals from a deviceaccording to the first or second preferred aspect of the invention, forexample signals from some or all of a plurality of such devices, forexample 2-10,000 or 10-1000 devices.

In a fifth preferred aspect, this invention provides a method ofobtaining information which comprises examining signals recorded by adevice according to the first or second preferred aspect of theinvention, for example signals recorded by some or all of a plurality ofsuch devices, for example 2-10,000 or 10-1000 devices.

In a sixth preferred aspect, this invention provides a method forcontrolling a function of a device according to the first or secondpreferred aspect of the invention, the method comprising sending signalsto the device.

n a seventh preferred aspect, this invention provides novel floatssuitable for use in the first or second preferred aspect of theinvention and for other purposes; novel swimmers suitable for use in thefirst or second preferred aspect of the invention and for otherpurposes; novel fin systems suitable for use in the first or secondpreferred aspect of the invention and for other purposes; and novel finssuitable for use in the first and second preferred aspects of theinvention and for other purposes.

In an eighth preferred aspect, this invention provides kits of partscomprising two or more of the components needed to assemble a deviceaccording to the first or second preferred aspect of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated by the accompanying drawings, which arediagrammatic and not to scale;

FIG. 1 is a diagram of a water vehicle;

FIGS. 2 and 3 are cross-sections of fins for use in certain embodiments;

FIG. 4 is a cross-section of a tether;

FIG. 5 is a block diagram of a control system;

FIG. 6 shows a path for a station-keeping water vehicle;

FIG. 7 is a perspective view of a water vehicle;

FIG. 8 shows different configurations of a fin in FIG. 7;

FIG. 9 is a perspective view of a water vehicle;

FIG. 10 is an enlarged perspective view of part of FIG. 9;

FIGS. 11A to 11D show different configurations of the fins in FIG. 9;

FIGS. 12-19 and 21 are side views of water vehicles;

FIG. 20 is a plan view of the water vehicle of FIG. 21;

FIGS. 22A to 22C show different configurations of a water vehicle havinga flexible body;

FIGS. 23-25 are perspective views of water vehicles;

FIGS. 26A to 26D show different views of a water vehicle; and

FIGS. 27A to 27D show different views of a water vehicle.

In some Figures, the fin system is numbered 0, 1, 2, 3 or 4. If theconfiguration is numbered 0, it is the configuration likely to beadopted when the vehicle is in still water. If the configuration isnumbered 1, it is the configuration likely to be adopted when float isfalling behind the wave crest, and the tension on the tether is falling(and may be zero). If the configuration is numbered 2, it is theconfiguration likely to be adopted when the float has fallen to thetrough of the wave, and the tension on the tether starts to increase. Ifthe configuration is numbered 3, it is the configuration likely to beadopted when the float is rising towards the top of a wave and thetether is at or close to its maximum tension for this particular cycle.If the configuration is numbered 4, it is the configuration likely to beadopted when the float is near the top of a wave crest and the tensionon the tether has decreased. It is to be understood, however, that theconfiguration of the fin system in practice will not necessarily be thatshown in the Figures.

DETAILED DESCRIPTION OF THE INVENTION

In the Summary of the Invention above, the Detailed Description of theInvention below, and the accompanying drawings, reference is made toparticular features of the invention. It is to be understood that thedisclosure of the invention in this specification includes all possiblecombinations of such particular features. For example, where aparticular feature is disclosed in the context of a particular aspect, aparticular embodiment, or a particular Figure, that feature can also beused, to the extent appropriate, in the context of other particularaspects, embodiments and Figures, and in the invention generally. It isalso to be understood that this invention includes all novel featuresdisclosed herein and is not limited to the preferred aspects of theinvention set out above.

The term “comprises” and grammatical equivalents thereof are used hereinto mean that other elements (i.e., components, ingredients, steps etc.)are optionally present. For example, a water vehicle “comprising” (or“which comprises”) components A, B and C can contain only components A,B and C, or can contain not only components A, B and C but also one ormore other components.

The term “at least” followed by a number is used herein to denote thestart of a range beginning with that number (which may be a range havingan upper limit or no upper limit, depending on the variable beingdefined). For example “at least 1” means 1 or more than 1, and “at least80%” means 80% or more than 80%.

The term “at most” followed by a number is used herein to denote the endof a range ending with that number (which may be a range having 1 or 0as its lower limit, or a range having no lower limit, depending upon thevariable being defined). For example, “at most 4” means 4 or less than4, and “at most 40%” means 40% or less than 40%.

When, in this specification, a range is given as “(a first number) to (asecond number)” or “(a first number)-(a second number)”, this means arange whose lower limit is the first number and whose upper limit is thesecond number. For example, “from 5 to 15 feet” or “5-15 feet” means arange whose lower limit is 5 feet and whose upper limit is 15 feet.

The terms “plural”, “multiple”, “plurality” and “multiplicity” are usedherein to denote two or more than two items.

Where reference is made herein to a method comprising two or moredefined steps, the defined steps can be carried out in any order orsimultaneously (except where the context excludes that possibility), andthe method can optionally include one or more other steps which arecarried out before any of the defined steps, between two of the definedsteps, or after all the defined steps (except where the context excludesthat possibility).

Where reference is made herein to “first” and “second” elements, this isgenerally done for identification purposes; unless the context requiresotherwise, the first and second elements can be the same or different,and reference to a first element does not mean that a second element isnecessarily present (though it may be present).

Where reference is made herein to “a” or “an” element, this does notexclude the possibility that there are two or more such elements (exceptwhere the context excludes that possibility). For example, wherereference is made herein to a fin, or a fin system, the swimmer can (andfrequently does) comprise two or more fins or fin systems, which may bethe same or different.

Where reference is made herein to two or more elements, this does notexclude the possibility that the two or more elements are replaced by alesser number or greater number of elements providing the same function(except where the context excludes that possibility). For example, theswimmer body and the fin system can together form a single unitary body.The numbers given herein should be construed with the latitudeappropriate to their context and expression; for example, each number issubject to variation which depends on the accuracy with which it can bemeasured by methods conventionally used by those skilled in the art.

Unless otherwise noted, the references to the positioning and shape of acomponent of the vehicle refer to that positioning and shape when thevehicle is in still water. Various terms are used in this specificationin accordance with the definitions given above and the furtherdefinitions given below.

“Leading edge” (or leading end) and “trailing edge” (or trailing end)denote the front and rear surfaces respectively of a fin or othercomponent as wave power causes the vehicle to move forward.

“Fore” and “aft” denote locations relatively near the leading andtrailing edges (or ends) respectively.

“Aligned” denotes a direction which lies generally in a vertical planewhich is parallel to the vertical plane which includes the longitudinalaxis of the swimmer. “Axially aligned” denotes a direction which liesgenerally in the vertical plane which includes the longitudinal axis ofthe swimmer.

“Transverse” denotes a direction which lies generally in a verticalplane orthogonal to the vertical plane which includes the axialcenterline of the swimmer.

Where reference is made herein to a feature which “generally” complieswith a particular definition, for example “generally in a verticalplane”, “generally laminar”, or “generally horizontal”, it is to beunderstood that the feature need not comply strictly with thatparticular definition, but rather can depart from that strict definitionby an amount which permits effective operation in accordance with theprinciples of the invention.

All the components of the vehicle, particularly any electricalconnections, are preferably constructed of materials which are resistantto salt water, and/or enclosed within a watertight jacket of suchmaterial. Preferably, the materials which are exposed to the water areresistant to bio-fouling, and are unattractive or even repellent tomarine animals, e.g., sharks. Suitable materials can for example beselected from metals and polymeric compositions, includingcopper-containing paints and low surface energy polymers such aspolytetrafluoroethylene. When the vehicle includes batteries and solarpanels (or other electricity-generating means), bio-fouling can also bediscouraged by using the power from the batteries or solar panels tobriefly electrify conductive materials on the vehicle, and/or toenergize a vibrator which will dislodge bio-fouling materials. Leadingedges which may be snagged by seaweed can optionally have sharp orserrated edges.

The vehicle is preferably designed to minimize drag as movement of theswimmer pulls it forward, and to minimize the effect of winds and watercurrents which move the vehicle sideways. The float or the swimmer orboth can have flaps which are folded-in and have little effect on dragwhen the float or swimmer is moving forward, but which fan out andincrease drag when the float or swimmer is moving backwards. Such flapsare preferably positioned so that they keep the float and/or the swimmerin a desired orientation if it moves backwards.

A preferred device having characteristic (B) above can for exampleinclude a fin system which comprises (1) a plurality of fins, forexample 3-10 or 4-6 fins, e.g., 5 fins, (2) a rigid bar which is mountedon the swimmer body, and to which each of the fins is rotatably mounted,and (3) an elastic component as defined in (B). The rigid bar ispreferably aligned with the longitudinal axis of the swimmer body. Thefins, which can be the same or different, preferably lie behind eachother (optionally in the same horizontal plane), and preferably each ofthe fins rotates about a transverse axis which is generally transverseto the longitudinal axis of the swimmer body. Each of the elasticcomponents influences the speed and/or the extent of the rotation of thefin to which it is linked. The elastic component can for example extendfrom a fixed point on the rigid bar, for example aft of the transverseaxis of the fin, to a fixed point on the fin, for example aft of thetransverse axis of the fin.

A preferred device having characteristics (A) and (B) above can forexample include (i) a generally laminar fin which is mounted, optionallyrotatably mounted, directly or indirectly on a rigid bar which ismounted, optionally rotationally mounted, on the swimmer body, and (ii)a spring and/or a torsion bar which is directly or indirectly connectedto the fin and/or to the rigid bar and which influences (a) the speedand/or the extent of the rotation of the fin and/or the rigid bar,and/or (b) the spatial relationship between the swimmer body and theaxis of rotation, during part or all of the changes in configuration ofthe system.

A preferred device having characteristic (C) above can for example havea fin system which comprises a generally laminar and elasticallydeformable fin (such a fin optionally being the sole elastic component,or one of a plurality of elastic components, of the fin system), the finhaving a leading edge which comprises (i) a relatively rigid centralsection which rotates about an axis of rotation generally transverse tothe longitudinal axis of the swimmer body, and (ii) relativelydeformable outboard sections (for example a fin having a swept back,e.g., generally V-shaped, leading edge),

The Swimmer Body

The swimmer body often has a generally cylindrical shape, or other shapeselected to minimize drag as the fin system pulls the swimmer throughthe water. Often there is a single swimmer body, but there can be aplurality of bodies secured to each other, preferably rigidly, withtheir axes aligned, or with their axes parallel to, and spaced-apartfrom, each other. Preferably the body has a longitudinal axis which isgenerally horizontal when the vehicle is in still water.

Usually, but not necessarily, the swimmer body has a length (i.e., thedimension measured along the longitudinal axis) substantially greaterthan its width (i.e., the dimension of the swimmer body measuredtransverse to the longitudinal axis). The length of the swimmer body canfor example be at least 1 foot (0.3 m), e.g., 3 to 10 feet (0.9 to 3 m)or 4 to 6 feet (1.2 to 1.9 m), but can be substantially greater, e.g.,up to 1000 feet (300 m) or more. The diameter (or, for non-cylindricalbodies, each of the minimum and maximum transverse dimensions) of theswimmer can for example be at least 0.1 feet (30 mm), or at least 0.3feet (90 m), up to, for example, 0.1 times the length of the swimmer.

In some embodiments the entire swimmer body will be rigid. However, itis also possible for part of the swimmer body to be elasticallydeformable. For example, the swimmer body can have a central sectionwhich is flexible, preferably substantially only in the vertical plane,with the rudder mounted on a rigid section aft of the flexible centralsection and the fin system mounted on a rigid section forward of theflexible central section. Optionally, the swimmer has a center ofbuoyancy which is above the center of gravity.

As further discussed below, a wide variety of additional components canbe attached to the swimmer body. Heavy components are preferably securedto the swimmer rather than to the float. The wet weight of the swimmer,including the components attached thereto, can for example be 5-20,000lbs (2-9,000 kg), e.g., 5-500 lbs (2-225 kg), for example 20-60 lbs(9-30 kg). Many components are preferably placed within a watertightenclosure provided by the swimmer body (for example electricalequipment, including batteries, electronic equipment, servo mechanisms,watertight pass-throughs, and direction-finding equipment). Others arepreferably or necessarily placed outside the swimmer body, for examplestabilizer fins, stabilizer weights, rudders, some types of sensor, andsample collectors.

Stabilizer fins, which can for example be placed near the front and/ornear the rear of the swimmer body, can for example be generally verticalfixed and aligned fins which resist transverse drag on the swimmer, orgenerally horizontal fixed and aligned fins which resist vertical dragon the swimmer. Stabilizer weights can for example be bars and/or discs,usually aligned with the swimmer body, fixed to struts descendingvertically from the swimmer body, thus increasing the weight andchanging the center of gravity of the swimmer, or can be part of akeel-like vertical stabilizer fin.

In one embodiment, a hydrophone is secured to the swimmer body.Preferably, in order to separate the hydrophone from noise generated bythe swimmer, the hydrophone is placed at the end of a cable draggedbehind the swimmer body, or on an extension bar projecting from, e.g.,from the front of, the swimmer body.

The Float

The float can be of any convenient size and shape, bearing in mind thecomponents which it carries, the way in which it will be used, and thedesirability of minimizing drag in the water and against wind. Thelength of the float can be less than, e.g., 0.5 to 0.9 times,substantially equal to, e.g., 0.9 to 1.1 times, or greater than, e.g.,1.1 to 4 times, the length of the swimmer. The length of the float canfor example be at least 1 foot (0.3 m), e.g., 3 to 10 feet (1-3 m) or 4to 6 feet (1.2-1.9 m), but can be substantially greater, e.g., up to1000 feet (300 m) or more, so long as it is not too large to besubstantially moved by waves. The breadth of the float can for examplebe at least 0.3 foot (1 m), or at least 2 feet (1.9 m), up to, forexample, 0.3 times the length of the float. Optionally, the float has acenter of buoyancy which is above the center of gravity. The float canfor example have 20-500 lbs (9-225 kg, e.g., about 80 lbs (36 kg), ofbuoyancy, and/or a buoyancy which is 2-4 times the wet weight of theswimmer.

To reduce the danger that wind, waves or current forces push the floatsideways, preferably both the center of water drag and the center ofwind drag are behind the line attachment point, since this helps to keepthe float in a head-on orientation in which it has the lowest overalldrag. Wind and water forces acting on the parts of the float forward ofthe tether attachment point tend to rotate the float away from thedesired orientation, whereas those aft of the attachment point tend toproduce the desired orientation. Therefore, the nose of the float ispreferably is relatively blunt and truncated, whereas the tail portionof the float preferably has an extended tail portion with greatervertical surface area.

The float may include a rudder. The rudder may be fixed during some orall of the operation of the vehicle, in order to keep the center of dragbehind the tether attachment point. The rudder may also be adjustable,in order to assist steering of the vehicle; in this case, the tether ispreferably attached to the swimmer in front of the swimmer's center ofdrag. Especially when the tether is attached slightly forward of thecenter of buoyancy of the float, the submerged surfaces of the float maybe shaped so as to produce forward thrust.

The float optionally comprises an outer shell comprising a polymericcomposition, e.g., a fiberglass- or carbon fiber-reinforced polymericcomposition, and/or a thick-walled elastomeric sheet material. The shellcan optionally surround a closed cell polymeric foam core, e.g., acompliant closed cell foam, and/or a plurality of hollow cavities. Insome embodiments, such cavities can optionally be inflatable (forexample being composed of an elastomeric material), so that they can bepartially or completely filled with water and/or air to controlbuoyancy.

The Tether

The tether connects the float and the swimmer mechanically, and for thispurpose comprises a tensile member of suitable breaking strength, e.g.,at least 500 lb (225 kg) or at least 1500 lb (675 kg). The tensilemember can for example be composed of a metal, e.g., stainless steel,and/or a polymeric composition, e.g., Kevlar or Spectra. Often, thetether also comprises one or more members which do not carry any loadand which transmit electrical power and/or data, e.g., one or moretwisted pairs of insulated electrical conductors, optical fibers oracoustic cables. Generally, the tether will support only tensile loads,but the invention includes the possibility that the tether will alsoresist compression, e.g., is a rod.

To reduce drag, the components of the tether are preferably arranged tominimize the area of the leading edge of the tether, with the primarytensile member at the front. Thus, the tether optionally includes ajacket, preferably of streamlined cross-section, e.g., composed of apolymeric composition, e.g., a composition based on a silicone or vinylchloride polymer, which surrounds the other components. Twisting of thetether increases drag, and optionally measures can be taken to reducetwisting. For example, a second tensile member can be present at thetrailing edge of the tether, and/or the vehicle can include a device todetect and correct twisting of the tether, and/or the vehicle can bedirected along a path in which the clockwise and anticlockwise turns arebalanced (in particular, when the vehicle is directed along a pathsurrounding a fixed point).

The tether can for example have an aligned dimension of 0.5 to 1.0 inch(13-25 mm), e.g., about 0.625 inch (16 mm, a transverse dimension of0.125 to 0.5 inch (3 to 13 m), e.g., about 0.19 inch (5 mm, and a lengthof for example 10 to 80 feet (3-25 m), e.g., 17 to 23 feet (5-7 m).Either the float or the swimmer can include a reel or other equipmentwhich makes it possible to change the length of the tether, either tosuit particular wave conditions and/or water depth, and/or to make thevehicle more easily stored, carried and deployed.

The tether can for example include an elastomeric member, e.g., aspring, which changes in length reversibly when the relative positionsof the float and swimmer change. For example, one leg of a tethergenerally shaped as an inverted Y can comprise such an elastomericmember.

In some embodiments, there is a single tether. The tether can forexample have a central section which is a single line, and a lowersection (attached to the swimmer) and/or an upper section (attached tothe float) which has two or more legs, secured to fore and aftpositions, or to transverse positions, on the swimmer or the float. Inone embodiment, the tether has the shape of an inverted Y, the lowerlegs of the Y being (a) aligned with, and secured to fore and aftpositions on, the swimmer, or (b) transverse to the swimmer and securedto components extending transversely from the axis of the swimmer.

When there is a single tether between the swimmer and the float, itsconfiguration and point of attachment (or points of attachment, if thetether has two or more lower legs) to the swimmer are preferably suchthat the upward force exerted on the swimmer, when the tether is pulledupwards, passes through the swimmer at or close to the center of gravityof the swimmer. The swimmer is then substantially horizontal when thevehicle is in still water. This assists the swimmer to maintain a levelorientation.

When there is a single tether between the swimmer and the float, itsconfiguration and point of attachment (or points of attachment, if thetether has two or more upper legs) to the float are preferably such thatthe downward force exerted on the float, when the tether is pulledupwards, passes through the float near, or slightly forward of, thecenter of buoyancy of the float.

In other embodiments, there are multiple tethers, for example first andsecond tethers respectively attached to fore and aft positions on thefloat and the swimmer. Multiple tethers increase drag, but reducetwisting.

The tension force of the tether stabilizes both the swimmer and thefloat. While each element may also be independently stabilized bypositioning of the center of flotation above the center of gravity, thisis not necessary. The fact that the line tension stabilizes both theswimmer and float simplifies the control of the vehicle. In someembodiments, the vehicle only needs to be steered in one degree offreedom, and other attitude control is passively stabilized, making itunnecessary for the vehicle to include attitude control thrusters orflaps (although such thrusters and flaps can be present).

The Fin Systems

When the swimmer is being moved by wave power, the configuration of thefin system changes in cycles corresponding to the waves on the surfaceof the water. Generally, but not necessarily, the changes in theconfiguration in each cycle are substantially the same. The changes inthe configuration in each cycle are generally substantially continuous,but can be discontinuous (i.e., there can be one or more periods in eachcycle during which the configuration remains the same). During at leastpart of the cycle, the fin system interacts with the water to generateforces which thrust the swimmer in a horizontal direction. In someembodiments, the fin system comprises a fin which rotates about atransverse axis. In other embodiments, the fin system comprises a pairof fins which rotate about a longitudinal axis. In either case, as theswimmer rises and falls, the fin or fins can optionally undergo elasticdistortion which enhances the forward thrust of the swimmer.

Different wave sizes will produce different responses from different finsystems. For example, with relatively large waves, the majority of thethrust often tends to be produced during the upward and downward phasesof fin motion, whereas with relatively small waves, the majority ofthrust tends to result from rotation of the fins. Flexible fins tend toproduce thrust from both small and large waves.

For any particular water vehicle of the invention, the influence of theswimmer on the movement of the float will depend in part on the size andfrequency of waves. The movement of the float will also depend forexample on environmental conditions such as water currents and wind, andany other propulsion or steering system operating on the float. Insuitable conditions, the swimmer will move the vehicle forward at aspeed which is satisfactory for many purposes, without any otherpropulsion system (though it may be desirable to use another powersource to operate a steering system).

The horizontal motion of the swimmer and float will often be cyclic,alternating between a glide phase and a kite phase, the float's peakhorizontal speed being during kite phase, and the swimmer's peakhorizontal speed being during the glide phase.

In the glide phase, the line tension is low and the swimmer is able toglide forward rapidly. The float may move forward slowly or not moveforward. During the kite phase, the line tension is high and, if theswimmer was successful at gliding forward during the glide phase, theline will be at an angle such that the increased tension slows theforward motion of the swimmer. The steep line angle and high tensionwill pull the float forward rapidly, partially catching up with theadvance the swimmer made during the glide phase.

Drag is proportional to the square of velocity. Since velocity of theswimmer is highest during the glide phase it is preferred to minimizedrag in this phase. Described below and in the attached FIGS. 27A-D isone example of a water vehicle which achieves low drag during glidephase and is able to transition from kite phase to glide phase quicklyand quietly. In this example, the swimmer body has a central bodystructure that is longest along a longitudinal axis. Fins extend fromeither side of the body and can rotate relative to the body about anaxis that is substantially perpendicular to the body longitudinal axisand preferably also to the tether axis. There may be one pair of wingswith a single axis, or multiple wing pairs. Preferably, the rotation ofthe fins is controlled in part by a spring which will resist rotation ineither direction from a rest position. One advantage of using such aspring is that it provides gently increasing resistance to rotationwithout producing the noise that results from sudden stops and which canprejudice the operation of sensitive acoustic instruments.

While the vehicle is at rest in still water, the tether is preferablygenerally vertical and is attached to the body so that the axis of thebody is as an angle of zero to 30°, preferably 3-10°, to the horizontal.The chord axis of the fin in the rest position is preferably generallyhorizontal.

When the line tension is released by the float moving down, the swimmerwill move down and the fluid pressure on the wing will cause it torotate to a glide position, while the spring resists this rotation. Thespring force and the lift force are balanced such that the angle of thewing in glide position is similar to the body longitudinal axis and thusprovides minimum drag. When the line tension is increased by the floatmoving up, the swimmer will move up and the fluid pressure on the wingwill cause it to rotate to a kite position, while the spring resiststhis rotation. The spring force and the lift force are balanced suchthat the wing operates at an efficient angle of attack during the kitemotion to produce forward thrust.

One example of an efficient wing shape for gliding has high aspect ratio(span/chord), an elliptical plan form, and a slender airfoil shape. Afin with a relatively short chord enables rapid rotations between glideangle and kite angle so that the fin can achieve optimal angle of attackfor each phase with minimum lost motion.

A single fin is shown in FIG. 27. Multiple fins are similarly possible,with each fin behaving in a similar manner. In addition to the primarythrust producing wing or wings, smaller tail wings or front canard wingsmay be provided for stability.

Controlling Angle of Glide

The optimum glide angle will vary depending on the sea state. If wind orsurface currents are pulling the float backwards, then a steep glideangle may be needed to achieve forward motion. Conversely, if the windsand currents are favorable, then a shallow glide angle can increasedistance traveled each glide cycle.

Active control may be applied to the angle of a tail wing or canard wingto control the glide angle. Alternatively, or in addition, the center ofgravity may be adjusted along the body axis by moving an internal mass.For example a lead screw drive may move the battery pack fore or aft toadjust the center of gravity. Alternatively or additionally, the tetherattachment may be adjusted to affect the body angle.

In preferred embodiments, the vehicle is equipped with control andsteering systems which enable it to be remotely controlled in a desiredway, for example so as to move in a closed pattern around a desiredfixed location, and/or to follow a desired path between two locations,which may be many miles apart, and/or to traverse slowly back and forthover an area of the ocean in order to gather a wide variety of data.

If the float is also moved by other forces (for example by wind, watercurrents or a conventional propulsion system) the movement of theswimmer modifies (for example accelerates or decelerates and/or changesthe direction of) the movement of the float.

Different fin systems which interact with the water in the desired wayinclude, but are not limited to, the various types described herein. Aparticular fin system can make use of combinations of two or more ofthese types, except when they are incompatible with each other; and awater vehicle can comprise two or more fin systems of the same ordifferent types or combinations of types. Where reference is made belowto a “generally laminar fin”, this includes the possibility that thethickness of the fin changes, regularly or irregularly, in thetransverse direction or in the aligned direction, or both, and thepossibility that parts of the fin extend outwards from its generallylaminar shape. For example, at least part of a fin can have an airfoilcross section, i.e., a cross-section such that the fin produces lift anddrag as it interacts with the wave-bearing water Where reference is madebelow to a generally laminar fin which “lies in a generally horizontalplane”, this includes the possibility that the principal plane of thefin lies in a plane which is inclined to the horizontal at an anglewhich permits effective operation of the fin, for example at an anglewhich is not more than 45°, preferably not more than 20°, to thehorizontal.

In some embodiments of the invention, part or all of the fin system hasa first configuration when the vehicle is in still water; is convertedfrom the first configuration into a second configuration when theswimmer is pulled upwards by the tether as a result of a wavecrestlifting the float upwards; and is converted from the secondconfiguration into a third configuration when the swimmer sinksdownwards as a result of a wavetrough allowing the float to descend. Thethird configuration will generally be different from the firstconfiguration, but the invention includes the possibility that it is thesame as the first configuration. When the fin system is converted fromthe second configuration to the third configuration, it can, but neednot, pass through the first configuration as a transitory state.

The fin system can for example comprise one or more fins comprisinggenerally laminar portions which deform elastically between thedifferent configurations. Alternatively or additionally, the fin systemcan for example comprise one or more elastically deformable components,which change shape between the different configurations, and thuscontrol, or help to control, the movement of fin or fins comprisinggenerally laminar portions. The elastically deformable component cancontrol, or help to control, the movement of a fin in one direction only(e.g., a spring) or in two or more directions, e.g., in both the upwardand downward direction (e.g., a torsion bar).

Limit stops may be included to prevent undesired movement of a fin, forexample to prevent excessive bending of a flexible fin. The stop may bea rigid stop, an elastic stop, e.g., a spring, including an increasingrate spring

The fin system comprises at least one fin, the fin preferably having oneor more of the following characteristics:

-   -   (a) It is at least in part elastically deformable.    -   (b) It is at least in part substantially rigid.    -   (c) It comprises a leading portion which is relatively rigid and        a central portion and/or a trailing portion which is relatively        and elastically deformable.    -   (d) It comprises a leading portion which is relatively and        elastically deformable, a central portion which is relatively        rigid, and a trailing portion which is relatively and        elastically deformable.    -   (e) It has a shape similar to the shape of the tail of a fish or        a whale.    -   (f) In the first configuration, it is generally planar in a        generally horizontal plane.    -   (g) In the second configuration, it is generally laminar and        downwardly curving, the second configuration being a result of        flexing and/or rotating the fin about an axis which lies in a        plane which is generally orthogonal to the tether and generally        at right angles to the longitudinal axis of the swimmer.    -   (h) When the swimmer sinks downwards as a result of a wavetrough        causing the float to fall, the fin system changes from the        second configuration to the third configuration, the third        configuration being generally laminar and upwardly curving.

Other optional features of the fin system include:

-   -   (1) It comprises a plurality of fins, which may be the same or        different, and which may be aligned in the same horizontal        plane, or which may be in two or more different planes.    -   (2) It comprises a plurality of fins which are mounted to a        frame, for example a plurality of fins mounted to both sides of        an axially aligned spine, or a plurality of fins mounted between        aligned side rails.    -   (3) It comprises a pair of fins, the fins        -   (i) extending away from opposite sides of the swimmer body,        -   (ii) being secured to the swimmer body so that they can move            between the first and second configurations, the position of            the fins in the second configuration extending upwards            relative to the position of the fins in the first            configuration, and        -   (iv) being biased by a spring or other elastic recovery            means into the first configuration and away from the second            configuration.    -   (4) The fin system comprises a pair of fins and the tether        comprises an inverted V-shaped section having two legs, each leg        being secured to one of the fins; and    -   (5) It comprises a caudal fin.

In the first aspect of the invention, the fin system optionallycomprises at least one additional member whose shape is fixed and issuch that that the additional member directly or indirectly generatesdesired horizontal forces as the swimmer is moved by the movement of thefloat. In one embodiment of the second aspect of the invention, suchmembers are the sole means for generating the desired forces.

The optimum amount of flexibility for a flexible fin will depend on manycharacteristics of the design and of the wave characteristicsanticipated. If the fin is too flexible, then the curvature during thelarge amplitude motion may be so large that the trailing portion of thefin may flex to be parallel to the direction of motion and thus generatelittle thrust. If the fin is too rigid, then the fin will not flex withany inflections and small amplitude inputs will not efficiently generatethrust. Those skilled in the art will have no difficulty, having regardto their own knowledge and the information contained in thisspecification, in determining a suitable amount of flexibility.

The fin system often includes a rigid component which is secured to,preferably positioned above, the body of the swimmer. The rigidcomponent can for example have one or more of the followingcharacteristics:

-   -   (i) It is rigidly fixed to the body portion.    -   (ii) It is positioned above the body portion and a unitary        tether, or one leg of a tether having an inverted Y        configuration, is secured thereto.    -   (iii) At least one fin system is secured thereto. When there is        more than one fin system, the systems can be mounted one above        the other and/or beside each other.    -   (iv) It is the first component of a support system which also        comprises a second rigid component. The first component is        positioned above, and secured directly to, the body portion in a        generally vertical plane and the second component is secured        directly to the first component and has one or more fin systems        secured thereto. The second component is optionally secured to        the first component so that it can rotate relative to the first        component in a generally vertical plane, and the rotation can        optionally be influenced by an elastically recoverable member,        e.g., a spring or a torsion bar. At least part of the tether is        optionally secured to the second component so that upward        pulling of the tether distorts the elastically recoverable        member. The extent of rotation is optionally further limited by        an inextensible member.        Water Vehicles with Pectoral Fins

In some embodiments, a generally planar fin or a pair of generallyplanar fins undergoes elastic deformation in the transverse direction(and may also undergo elastic deformation in the aligned direction). Insome cases, such fins can move vertically without substantial verticalmotion of the swimmer body. They flap in a manner similar to thepectoral fins on a fish, or the wings on a bird. Preferably the pectoralfin or fins rotate about an axially aligned longitudinal axis.Optionally, the pectoral fin surfaces can also rotate and/or flexrelative to the horizontal plane or relative to a plane that intersectsthe longitudinal axis and an axis through the wing spar.

Pectoral fins of this kind are preferably directly actuated by thetether, thus reducing motion of the swimmer body. In some cases, thismakes them well suited for large swimmers or for applications where theswimmer body should be held relatively steady.

By attaching the legs of the tether to different points along the lengthof the pectoral fins, the amount of fin motion relative to the amount ofline motion may be adjusted.

Pectoral fins may for example have an internal skeletal structure madeof a less flexible, optionally substantially rigid, material with highfatigue life such as tempered steel or carbon fiber composite. Theskeletal structure can include a front spar that makes the leading edgerelatively rigid. The primary flexion of the skeletal structure occursin vertical bending of the front spar near the attachment to the body.The rigidity of the front spar may increase toward the outer parts toprevent the wing tips from drooping. The trailing edge of the wing canfor example be comprised only of the elastomer jacket material and berelatively flexible.

The tether is preferably attached to the pectoral wings at two points,one on each wing. The wing structure is preferably such that when thetether is not under tension, the fin flexes downward; and when thevehicle is in still water, the fins flex to a relatively flat position.Increased line tension will cause the wings to flex upward. The lineattachment points are preferably toward the front edge of the pectoralwings. The center of gravity (COG) is preferably under the line junctionpoint so that the swimmer body is horizontal in still water. If there ismore fin area behind the line attachment, upward motion will cause theswimmer to pitch nose up. If there is more fin area is behind the COG,downward motion will cause the swimmer to pitch nose down. Optionally, arudder steers the swimmer. Optional features of devices having pectoralwings can include:

-   -   (a) A smooth outer body which has no exposed mechanism and is        resistant to fouling.    -   (b) Flexion distributed over a large area so that fatigue at        specific points can be minimized for long life.    -   (c) A streamlined overall shape which enables increased speed.    -   (d) Sudden increases in tether tension are transmitted        immediately to fins so that the inertia of the vehicle does not        impeded conversion to thrust.    -   (e) The tips of the fins extend beyond the line attachment        points and the wing spar is relatively rigid in this region, so        that the tips of the fins move through a larger amplitude than        the tether. This helps generate large amounts of thrust from        small amounts of tether motion.

Additional Components.

Additional components which can be part of the water vehicle include,but are not limited to, those described in paragraphs 1-14 below. Somecomponents, e.g., electronic control equipment, can be part of either orboth of the float and the swimmer. Bulky or massive items, e.g.,batteries, and equipment that operates best with limited motion and/orwhen protected from wind and noise, such as imaging or mappingequipment, and hydrophones and sonar equipment, are preferably part ofthe swimmer. Other components, e.g., solar collection means, radio andnavigation antenna, beacons and weather sensors are preferably part ofthe float.

-   -   (1) Communications equipment for sending and/or receiving data,        e.g., digital or analog radio signals, for example        communications equipment for        -   (i) sending signals which reflect data collected by a            monitoring or sensing device which is part of the vehicle;        -   (ii) receiving signals, e.g., commands, from a base station            (e.g., a ship or a ground station) or from navigation            devices, for example satellite navigation equipment such as            a global positioning satellite (GPS), or sonar or radio            buoys,        -   (iii) sending signals to a receiving station, for example            via a satellite,        -   (iv) sending signals which are influenced by the location of            the vehicle.    -   (2) Recording equipment for recording signals, e.g., digital or        analog signals, for example signals which are        -   (i) influenced by signals from a satellite navigation            system, e.g., GPS;        -   (ii) sent from the vehicle to a receiving station, for            example via a satellite; (iii) influenced by the location of            the vehicle; or        -   (iv) influenced by a sensor which is part of the vehicle,            e.g., a hydrophone attached to the swimmer;    -   (3) Control electronics for controlling equipment forming part        of the vehicle.    -   (4) Steering means, for example a rudder forming part of the        float and/or a rudder forming part of the swimmer, the steering        means being for example a fixed rudder on the float (e.g., to        keep the center of drag behind the point at which the tether is        attached to the float), and/or a rudder or other steering means        which is attached to the swimmer and which includes a rudder        actuator responsive to signals generated within the vehicle,        e.g., from a magnetic compass or a gyroscope, and/or received by        communications equipment forming part of the vehicle.    -   (5) Electrical power sources, for example batteries or fuel        cells, preferably power sources that can be recharged, for        example by output from solar cells mounted on the float.        Batteries, because they are heavy, are preferably placed within        the container body of the swimmer. There can be, for example,        four to ten 6 volt lead acid batteries.    -   (6) Means for utilizing solar energy, e.g., solar panels or        solar cells mounted on the float.    -   (7) A sensor, this term being used to denote any device which        reports, or responds to a change in, any observable condition.        Thus the sensor can be any one of a large variety of scientific        or surveillance devices, for example a compass, a gyroscope, a        temperature sensor, a pressure sensor, a sensor of any type of        electromagnetic radiation, e.g., visible, ultraviolet or        infrared light, a chemical sensor, e.g., a salinity sensor, a        magnetometer, a biological sensor, a geological sensor, a water        current sensor, a depth sensor, a speedometer, equipment for        imaging the sea floor, a sensor of weather or other climatic        changes, e.g., windspeed, rainfall, or barometric pressure, or a        hydrophone (for example a hydrophone for monitoring the sounds        made by whales or other aquatic life).

In some embodiments, because the vehicles of the invention do not needto include conventional propulsion components, or other noisycomponents, they provide excellent platforms for noise-sensitive devicesand do not have any adverse effect on noise-sensitive devices carried byother equipment, e.g., other water vehicles.

-   -   (8) Auxiliary propulsion means, e.g., a motor-driven thruster.    -   (9) Auxiliary attitude control means, e.g., flaps.    -   (10) Means for reversibly altering the buoyancy of the float.        Such means include, for example, chambers which can be inflated        with air to increase buoyancy and deflated to reduce buoyancy,        and/or chambers which can be filled with water to decrease        buoyancy and evacuated to increase buoyancy. In this way, the        float can be maintained at a desired level in the water        (including submerged). Reducing buoyancy is valuable, for        example, when adverse weather conditions might endanger the        vehicle, particularly if the vehicle is relatively small. Such        chambers can for example comprise valves, e.g., one-way valves,        which are controlled by computers responding to input from        sensors on the vehicle itself or from radio signals. The energy        needed to inflate and/or to evacuate such chambers can be        derived directly from waves striking the float, and/or from the        wave power generated by the relative movement of the float and        the swimmer, and/or from stored electrical power. For example, a        chamber can comprise a flexible portion which will act as a pump        when struck by waves, and which will either fill or empty the        chamber, depending upon the position of the valves.        Alternatively or additionally, the float can comprise one or        more chambers with the one or more inlets through which water        can enter when waves are high but not when waves are low, and        one or more outlets from which the water can drain when waves        are low.    -   (11) Equipment for collecting samples, for example samples of        water, air, aquatic organisms, sea animals, vegetables or        minerals.    -   (12) Equipment for utilizing wind energy, e.g., to recharge        batteries.    -   (13) Auxiliary electrical equipment, for example lights,        beacons, or a motor driving a propeller.    -   (14) Means for converting part or all of the movement of the        swimmer into electrical energy.

In some embodiments, it is possible to operate simultaneously surfacecomponents, e.g., solar cells and/or radio, and a submerged component,so that data transmission can be “real time”. It is also possible toplan alternating phases of data collection and transmission.

Directing the Vehicle Along a Desired Path

In some uses of the invention, the vehicle is directed along a desiredgeographical path with the aid of a computer attached to the float orthe swimmer. The computer is used for example

-   -   (a) to process (i) input from a magnetic compass or gyroscope        (preferably attached to the swimmer), (ii) input from a        satellite navigation system, e.g., GPS (preferably attached to        the float), and (iii) geographical coordinates preprogrammed        into the computer and/or input to the computer by radio        commands; and    -   (b) to output commands to (i) a rudder control system which        controls a rudder or rudders on one or both of the float and the        swimmer, preferably on the swimmer, and (ii), if the vehicle has        auxiliary control or propulsion means, to those means. The input        to the computer can include data available from other sources,        e.g., to take account of winds and currents.

In other uses of the invention, the vehicle is directed along a pathwhich is determined by using a computer attached to the float or theswimmer, or both, the computer being used to

-   -   (a) process input from a sensor attached to the vehicle itself,        or from a network of vehicles, one or more of which are vehicles        of the invention, and    -   (b) output commands to (i) a rudder control system which        controls a rudder or rudders on one or both of the float and the        swimmer, preferably on the swimmer, and (ii), if the vehicle has        auxiliary control or propulsion means, to those means.

In this way, for example, a hydrophone, magnetometer or other sensor onthe vehicle could identify the presence of an object in or on the wateror on the seabed, e.g., a ship or other floating or submerged object, ora whale or other sea creature, and the vehicle could be directed tofollow a path related to that object, e.g., to track the movement orpresence of that object.

The operation of the vehicle can be controlled by signals sent to itfrom a remote control station and/or by signals generated by the vehicleitself, optionally in conjunction with one or more preprogrammed commandstructures forming part of the vehicle itself. One way of keeping thevehicle close to a fixed point (“station-keeping”) is to direct thevehicle towards the fixed point at regular intervals, e.g., of 1-10minutes. If the vehicle has overshot the fixed point, it turns at theend of the interval. Successive turns are preferably clockwise andanticlockwise, to reduce the risk of twisting the tether, and each ofthe turns is preferably as small as is consistent with the avoidance oftwisting the tether. Another way is to direct the vehicle along agenerally figure-of-eight path, with the center of the path being thefixed point, and with the vertical axis of the path aligned with anyocean current. The vehicle follows a straight line between each of theturns, and again successive turns are clockwise and anticlockwise; and,if the time spent outside a zone defined by the straight sections of thepath is important, each of the turns is preferably as small as isconsistent with the avoidance of twisting the tether.

In many applications, it is unnecessary to control the speed of thevehicle. However, if such control is desired, it can for example beprovided by measures such as controlling the angle of attack of fins,allowing the fins to feather, and holding the fins stiff, to decreasetheir efficiency when less thrust is desired. If there are fins on eachside of the swimmer body, these measures can also be used to steer theswimmer.

Storage and Deployment

In order to make the swimmer easier to store and transport, theattachment point between the fin and the swimmer body may include apivot joint that allows the swimmer to be stored with the fin axisparallel to the body axis, e.g., in a canister, but allows the fin to berotated 90° into its operating position. This joint may be sprung andequipped with a detent or the like, so that after the fin can be lockedin the operating position.

The Drawings.

FIG. 1 shows a float 11 is connected to a swimmer 21 by a tether 31. Thefloat comprises a body 111 on which are mounted solar panels 112, GPSreceiver 113, antennae 114, and electronics box 115. A rudder 116 issecured to the rear of the float. Tether 31, having an inverted Y shapewith lower legs and 311 and 312, connects the float and the swimmer. Theswimmer comprises a body 211 having a nose cone 212. Mounted on theexterior of the body 211 are fin systems 213 and 214. Enclosed withinthe body 211 are electrical pass-through 215 for leg 311 of the tether,batteries 216, control electronics 217, rudder servo mechanism 218 andrudder rod pass-through 219. A rudder 222 is mounted at the rear of theswimmer body and is controlled by rudder actuation rod 221.

FIGS. 2 and 3 are cross-sections of fins which can be used in thepresent invention. Each comprises a rigid front spar 2131, which may forexample be composed of a sheet metal sandwich composite and/or have asteel core, a relatively inflexible central sheet section 2134, whichmay for example be composed of metal and/or fiberglass, and a relativelyflexible trailing sheet section 2135. In FIG. 3, there is in addition arelatively flexible fore sheet section 2133, and the flexible trailingsheet is integral with a flexible outer jacket 2136. The varioussections may be bonded or held together with fasteners such as rivets2132

FIG. 4 is a cross-section of a tether 31 which comprises a tensilemember 313, six twisted pairs of insulated electrical conductors 314,and a streamlined polymeric jacket 315.

FIG. 5 is a block diagram of a control system for directing the vehiclealong a desired path. Other control systems can be used.

FIG. 6 shows a generally figure-of-eight path followed repetitiously bya vehicle to keep it within a target zone around a fixed point 2 (exceptwhen it is turning outside the zone). The axis of the path is alignedwith the ocean current. The vehicle follows a straight path betweenpoints 1 and 3, passing through point 2. At point 3, control systems onthe vehicle note that the vehicle has reached the perimeter of thetarget zone, and operate a rudder so that the vehicle turnsanticlockwise between points 3 and 4. The vehicle then follows astraight path between points 4 and 5, again passing through point 2. Atpoint 5, the control systems operate the rudder so that the vehicleturns clockwise between points 5 and 1. If the vehicle is moved by windand/or current in addition to wave power, auxiliary propulsion means maybe needed to maintain the vehicle within the target zone.

FIG. 7 is a perspective view of a swimmer 21 and tether 31. Twosubstantially identical fin systems, each comprising a rigid verticalpost 226 and a fin 213, are secured to swimmer body 211. Tether legs 311and 312 are attached to the tops of the posts 226. Each fin comprises arelatively rigid front spar 2131 and a relatively flexible rear section2135 shaped so that the fin can operate without striking the swimmerbody; the fin optionally includes one or more intermediate sections (notshown) having relatively greater or lesser flexibility.

A hinge structure 2262 is bolted to each front spar 2131 and rotatesaround pivot shafts secured to the posts 226. Each of four torsion bars2263 is fixed at one end to one of the vertical posts and at the otherend to a front spar as a location selected to provide a desired degreeof control over the rotation of the front spar. Each fin can for examplehave a cross-section generally as shown in FIG. 2 or FIG. 3. Rigidvertical fins 222 and 223 are secured to the trailing and leading endsrespectively of the swimmer body. Fin 223 is fixed. Fin 222 can becontrolled to rotate about a vertical axis.

FIG. 8 shows how the shape of the fins in FIG. 7 changes as the swimmeris pulled up and down by wave motion.

FIG. 9 is a perspective view of a swimmer 21 and tether 31, and FIG. 10is an enlarged perspective view of part of FIG. 9. Two substantiallyidentical fin systems, each comprising a rigid vertical post 226 and afin 213, are secured to swimmer body 211. Each fin comprises arelatively rigid front spar 2131 and a relatively flexible rear section2135 shaped so that the fin can operate without striking the swimmerbody; the fin optionally includes one or more intermediate sections (notshown) having relatively greater or lesser flexibility.

A hinge bar 2262 is bolted to each front spar 2131. Bars 2265 aresecured to the hinge bars 2262. One end of each bar 2265 is rotationallysecured to a pivot shaft at the top of one of the posts 226, and theother end is rotationally secured to longitudinal bar 2266 which joinsthe bars 2265 attached to the respective posts. Springs 2267 are securedto the swimmer body and to the bar 2266. Tether 31 is secured to thelongitudinal bar 2266. Rigid vertical fins 222 and 223 are secured tothe trailing and leading ends respectively of the swimmer body. Fin 223is fixed. Fin 222 can be controlled to rotate about a vertical axis. Ina similar embodiment (not shown), the springs are rotationally attachedto the bars 2265 instead of the bar 2266.

FIGS. 11A to 11D show how the shape of the fins in FIG. 9 changes as theswimmer is pulled up and down by wave motion. In FIG. 11A, the swimmeris being pulled upwards; the tether tension increases and pulls the bar2266 upwards, stretching the springs 2267; the leading edges of the finsrotate downwards, and the trailing sections of the fins curl upwards,producing thrust from the bottom surfaces of the fins; and the swimmerbody moves upwards. In FIG. 11B, the tether tension remains high; afterthe rotation of the leading edge of the fin reaches its mechanicallimit, and the trailing sections of the fins curl downwards, producingthrust from the top surface of the fin; the swimmer continues to rise.

In FIG. 11C, the tether tension has decreased; the springs 2267 pull thebar 2266 downwards; the leading sections of the fins rotate upwards, andthe trailing sections of the fins curl downwards, producing thrust fromthe top surfaces of the fins; and the swimmer moves downwards. In FIG.11D, the tether tension remains low; the leading sections of the finsremain rotated upwards, and the trailing sections of the fins curlupwards, producing thrust from the bottom surfaces of the fins; and theswimmer continues to move downwards.

FIGS. 12-21 show the swimmer of different water vehicles of theinvention. In each, a swimmer 21 has a center of gravity 230 andcomprises a swimmer body 211, a nose cone 212 and a rudder 222. Securedto the swimmer body is a fin system comprising vertical post(s) 226 andone or more fins, each fin comprising two or more of flexible innersection 2133, rigid section 2134 and flexible outer section 2135.

In FIGS. 12-16, there is a single post, and a tether 31 is secured tothe top of the post. In FIGS. 12-14, the leading edge of a single fin isfixed to an intermediate position on the post. In FIGS. 15 and 16, theleading edge of a single fin is rotatably secured about pivot point 2261at an intermediate position on the post. In FIG. 16, stop 2268 limitsrotation of the leading edge of the fin.

In FIG. 17, there is a single post having a bar 2265 rotatably securedto its top. The leading edge of the fin is secured to one end of the bar2265, and tether 31 is secured to the other end of the bar 2265.Rotation of the bar 2265 is controlled by spring 2267 secured to thepost and the bar. FIG. 18 is similar to FIG. 17, except that there arethree bars 2265 with attached fins, the tether 31 is secured to the topbar, and a line secured to the tops of all three bars and to the swimmerbody includes the spring 2267. FIG. 19 is somewhat similar to FIG. 18,except that the three bars 2265 with attached fins are arrangedhorizontally and each has one end rotatably secured to a lowerhorizontal bar attached to two vertical posts 226 and the other endrotatably secured to an upper horizontal bar to 266. Rotation of thebars 2265 is controlled by spring 2267 which is secured to the upperhorizontal bar and the swimmer body.

In FIGS. 20 and 21, there is a single post having a bar 2265 rotatablysecured to its top. The leading edge of the fin is secured to one end ofthe bar 2265. The lower legs 311 and 312 of tether 31 are secured to theends of the bar 2265, and leg 312 includes spring 2267. Rotation of thebar 2265 is limited by flexible line 2268. Fixed horizontal stabilizerfin 225 is secured to the trailing end of the swimmer body.

FIGS. 22A-22C show the different configurations of a swimmer comprisinga swimmer body 21 having a rigid rear section 214 having horizontalfixed stabilizer 225 secured thereto; a central section 228 which can bedeformed elastically in the vertical plane but not substantiallydeformed in the horizontal plane; and a rigid front section 212 to whicha rigid fin 213 is secured. A tether 31 is secured to front section 212.In FIG. 22A, the swimmer is in still water. In FIG. 22B, the swimmer isbeing pulled upwards. In FIG. 22C, the tether tension has dropped, andthe weight of the swimmer is forward of the center of lift, causing thefront section to tilt downwards.

FIG. 23 shows a swimmer which operates in a way similar to the swimmershown in FIG. 22. The rigid fin 213 rotates relative to rigid swimmerbody 211, and the tether is attached to the top of a post 226 whichrotates relative to the fin and the swimmer body, and which carries astabilizing weight 226 at its bottom end.

FIGS. 24 and 25 show swimmers in which the fin system comprises two fins233 which rotates about an aligned axis and are connected, at pointsoutboard of the swimmer body, to transverse bottom legs 315 and 316 oftether 31. The swimmer shown in FIG. 24 also comprises rigid fixedvertical fins 223 at the leading end of the swimmer body.

FIGS. 26A, 26B and 26C are top, side and front views of the swimmer of awater vehicle, and FIG. 26D is an enlarged view of the front of FIG.26B. The Figures show a tether 31; a swimmer body 211 having a nose cone212, a rudder 222 and a COG 230; and a fin system comprising verticalposts 226, horizontal bar 2265, and a plurality of identical fins. Eachfin is rotatably attached to the bar 2265 at a pivot point 2261 and isalso secured to the bar 2265 by springs 2267 which control the rotationof the fin. Each fin comprises a substantially rigid leading edge 2131,a relatively inflexible central section 2134, and a relatively flexibletrailing section 2135. In similar embodiments, the number of fins could,for example, be from 3 to 8, e.g., 5, and the bar 2265 and the springs2267 could be configured so that the movement of each fin is controlledby a single spring.

FIGS. 27A-D show different attitudes of a swimmer as it moves throughdifferent phases of its interaction with the water. The vehiclecomprises a float 11, a tether 31, and a swimmer 21 which comprises abody 211 and a fin which extends on both sides of the body 211. The finrotates about a fin axis 2137 which is at right angles to the axis ofthe tether and at right angles to the swimmer body axis 2117. The finhas a chord axis 2138 which is parallel to the body axis 2117 when thevehicle is at rest (FIG. 27A) and during the glide phase (FIG. 27C), andis at an angle to the body axis 2117 during the kite phase (FIG. 27D).

1. A wave-powered water vehicle which comprises: (1) a float, (2) aswimmer, and (3) a tether connecting the float and the swimmer; thefloat, swimmer and tether being such that, when the vehicle is in stillwater, (i) the float is on or near the surface of the water, (ii) theswimmer is submerged below the float, and (iii) the tether is undertension; the swimmer comprising (2a) a swimmer body having alongitudinal axis, and (2b) a fin system which (a) is secured to thebody, (b) comprises a fin, and (c) when the vehicle is in wave-bearingwater, (i) has a configuration which changes as a result of the wavemotion, and (ii) interacts with the water to generate forces which tendto move the swimmer in a horizontal direction.
 2. A water vehicleaccording to claim 1 in which the fin system has one or more of thefollowing characteristics: (A) it comprises a fin which rotates about anaxis of rotation, the axis of rotation having a spatial relationship tothe swimmer body which changes when the vehicle is in wave-bearingwater; (B) it comprises (i) a fin which rotates about an axis ofrotation, and (ii) an elastic component which is not part of the fin,and which deforms elastically and thus influences changes in theconfiguration of the fin system when the vehicle is in wave-bearingwater; (C) it comprises a fin having a leading edge which comprises (i)a relatively rigid central section which has a fixed spatialrelationship with the swimmer body, and (ii) relatively deformableoutboard sections; and (D) it comprises two generally laminar fins, eachof which rotates about an axis of rotation generally aligned with thelongitudinal axis of the swimmer body.
 3. A water vehicle according toclaim 1 wherein the tether has one or both of the followingcharacteristics: (E) it comprises an elastically deformable member; and(F) it comprises a component which transmits data and/or electricalpower.
 4. A water vehicle according to claim 1 wherein the swimmer bodyhas one or more of the following characteristics: (G) it has asubstantially rigid fore section, a midsection which is relativelyflexible in the vertical plane, and a substantially rigid aft section;(H) it comprises one or more components selected from electricalequipment, communications equipment, recording equipment, controlelectronics, steering equipment, and sensors; (I) it comprises a finwhich influences the orientation of the swimmer body in the horizontalplane when the device is in the water-bearing water; (J) it comprises agenerally tubular housing and the fin system comprises fins which extendeither side of the housing; and (K) it comprises a generally tubularhousing and vertical fin surfaces respectively adjacent to the leadingend and the trailing end of the swimmer body.
 5. A water vehicleaccording to claim 1 wherein the fin system comprises: (1) a pluralityof fins, (2) a rigid bar which is mounted on the swimmer body, and towhich each of the fins is rotatably mounted, and (3) an elasticcomponent which is not part of a fin and which deforms elastically andthus influences changes in the configuration of the system when thedevice is in wave-bearing water.
 6. A water vehicle according to claim 1wherein the fin system comprises: (1) a rigid bar which is mounted onthe swimmer body, (2) a generally laminar fin which is mounted on therigid bar, and (3) an elastic component which is connected to the finand to the rigid bar.
 7. A water vehicle according to claim 1 whereinthe fin system comprises a generally laminar and elastically deformablefin having a leading edge which comprises (i) a relatively rigid centralsection which rotates about an axis of rotation generally transverse tothe longitudinal axis of the swimmer body, and (ii) relativelydeformable outboard sections.
 8. A water vehicle according to claim 1wherein: (1) the float comprises a satellite-based position sensor and(2) the swimmer comprises (a) a horizontal sensor which senses directionin a horizontal plane, and (b) a steering actuator; and the vehiclefurther comprises a computer system which (a) is linked to the positionsensor, the horizontal sensor and the rudder, (b) contains, or isprogrammable to contain, instructions to control the steering actuatorin response to signals received from the position sensor and thehorizontal sensor, or in response to signals received from a sensor onthe vehicle.
 9. A water vehicle according to claim 1 wherein: theswimmer has a center of gravity, and the tether is attached to theswimmer substantially vertically above the center of gravity; the floathas a center of buoyancy, and the tether is attached to the floatsubstantially vertically below the center of buoyancy; and the float hasa center of drag, and the tether is attached to the float in front ofthe center of drag.
 10. A method of utilizing wave power which comprisesplacing a water vehicle according to claim 1 in a body of water whichhas or which is expected to have water waves traveling across itssurface.
 11. A method of obtaining information which comprises analyzinginformation obtained from, or recorded by, a water vehicle as defined inclaim
 1. 12. A method for controlling a function of a water vehicleaccording to claim 1 which comprises sending signals to the watervehicle.